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A General Algorithm For The Numerical Solution Of Hypersingular Boundary Integral Equations, Massimo Guiggiani, Geeta Krishnasamy, Thomas J. Rudolphi, F. J. Rizzo 2017 Università di Pisa

A General Algorithm For The Numerical Solution Of Hypersingular Boundary Integral Equations, Massimo Guiggiani, Geeta Krishnasamy, Thomas J. Rudolphi, F. J. Rizzo

Thomas Rudolphi

The limiting process that leads to the formulation of hypersingular boundary integral equations is first discussed in detail. It is shown that boundary integral equations with hypersingular kernels are perfectly meaningful even at non-smooth boundary points, and that special interpretations of the integrals involved are not necessary. Careful analysis of the limiting process has also strong relevance for the development of an appropriate numerical algorithm. In the second part, a new general method for the evaluation of hypersingular surface integrals in the boundary element method (BEM) is presented. The proposed method can be systematically applied in any BEM analysis, either ...


Boundary Element Solutions To Wave Scattering By Surface Irregularities On A Fluid-Solid Interface, S. Shenoy, Thomas J. Rudolphi, F. J. Rizzo 2017 Iowa State University

Boundary Element Solutions To Wave Scattering By Surface Irregularities On A Fluid-Solid Interface, S. Shenoy, Thomas J. Rudolphi, F. J. Rizzo

Thomas Rudolphi

The boundary element method is used to solve fluid-solid half-space problems with fluid-filled dimples and air bubbles on the solid surface. The problems, formulated in the Fourier (frequency) domain, are described by the fullspace three-dimensional acoustic and elastodynamic boundary integral equations (BIE), with pressure and displacement serving as primary variables. The techniques developed are general and may be with any kind of incident wave, however, plane waves are used in all numerical experiments. The equations governing the acoustic region are first converted mathematically to equations like those of an elastic region. The two regions are coupled and solved for the ...


Variable Input Space Observer For Structural Health Monitoring Of High-Rate Systems, Jonathan Hong, Simon Laflamme, Jacob Dodson 2016 Iowa State University

Variable Input Space Observer For Structural Health Monitoring Of High-Rate Systems, Jonathan Hong, Simon Laflamme, Jacob Dodson

Simon Laflamme

Some engineering systems experiencing high-rate dynamic events, including air bags, debris detection, and active blast protection systems, could benefit from high-rate real-time observers for enhanced performance. However, the task of high-rate state estimation is challenging, in particular for real-time applications where the rate of the observer’s convergence needs to be in the microsecond range. This paper discusses critical challenges in designing highrate observers, and argues that adaptive observers are promising at the task of state estimation, and that they could be applied at high-rates provided the development of strategies to substantially increase their convergence. A novel adaptive observer termed ...


Cubesat Adcs Validation And Testing Apparatus, Jacob Stevens 2016 Western Michigan University

Cubesat Adcs Validation And Testing Apparatus, Jacob Stevens

Honors Theses

The WALI team at Western Michigan University requested a test environment to validate their CubeSat’s de-tumbling control system and hardware. The test environment required a Helmholtz cage and spherical air bearing. The Helmholtz cage provides an adjustable magnetic field to simulate low earth orbit; the spherical air bearing simulates the friction free environment the CubeSat will experience in space. In conjunction, the two components create an adjustable system that simulates a satellite in low earth orbit.


Microstructural Analysis Of Thermoelastic Response, Nonlinear Creep, And Pervasive Cracking In Heterogeneous Materials, Alden C. Cook 2016 University of Maine

Microstructural Analysis Of Thermoelastic Response, Nonlinear Creep, And Pervasive Cracking In Heterogeneous Materials, Alden C. Cook

Electronic Theses and Dissertations

This dissertation is concerned with the development of robust numerical solution procedures for the generalized micromechanical analysis of linear and nonlinear constitutive behavior in heterogeneous materials. Although the methods developed are applicable in many engineering, geological, and materials science fields, three main areas are explored in this work. First, a numerical methodology is presented for the thermomechanical analysis of heterogeneous materials with a special focus on real polycrystalline microstructures obtained using electron backscatter diffraction techniques. Asymptotic expansion homogenization and finite element analysis are employed for micromechanical analysis of polycrystalline materials. Effective thermoelastic properties of polycrystalline materials are determined and compared ...


Nanostructured Morphologies In Glassy Polymer Networks, Brian Greenhoe 2016 University of Southern Mississippi

Nanostructured Morphologies In Glassy Polymer Networks, Brian Greenhoe

Dissertations

The body of this work describes a novel approach for the dispersion of multi-walled carbon nanotubes in a high Tg epoxy prepolymer matrix using a twin screw high-shear continuous reactor. The method demonstrated improves on previous dispersion methods in several ways. It offers increased efficiency through excellent heat transfer, while being solvent-less, scale-able, and tailorable to drive dispersion states to judiciously chosen dispersion states. Furthermore, it was shown that dispersion state and agglomerate morphology can be directed, in several ways, through processing conditions and also by controlling the matrix viscosity profile through cure. Broadband dielectric spectroscopy, optical hot-stage microscopy ...


Development Of Cal Poly's Shock Table, Christopher D. Risner 2016 California Polytechnic State University - San Luis Obispo

Development Of Cal Poly's Shock Table, Christopher D. Risner

Master's Theses and Project Reports

Shock is one of the environmental tests that a spacecraft must pass before being cleared for launch. Shock testing poses a challenging data acquisition issue and careful selection of equipment is crucial to creating a successful shock test facility. Cal Poly’s CubeSat programs can currently perform all environmental testing other than shock themselves, so a quality shock table would be useful. Previous groups of students had developed a shock table, and this paper details the improvement and characterization of that shock table’s behavior. Several adjustable parameters were tested and documented to discover trends in the shock table’s ...


Simulation Investigation Of Temperature Distribution In Large Aluminium Panel During Autoclave Age Forming Process, Yongqian Xu 2016 Central South University

Simulation Investigation Of Temperature Distribution In Large Aluminium Panel During Autoclave Age Forming Process, Yongqian Xu

The 8th International Conference on Physical and Numerical Simulation of Materials Processing

No abstract provided.


Multi-Dome Forming Of A Ti–Al–Mn Alloy, Sergey Aksenov, Aleksey Kolesnikov, Ivan Zakhariev 2016 National Research University Higher School of Economics

Multi-Dome Forming Of A Ti–Al–Mn Alloy, Sergey Aksenov, Aleksey Kolesnikov, Ivan Zakhariev

The 8th International Conference on Physical and Numerical Simulation of Materials Processing

No abstract provided.


Synthetic Defects For Vibrothermography, Jeremy Blake Renshaw, Stephen D. Holland, R. Bruce Thompson, David J. Eisenmann 2016 Iowa State University

Synthetic Defects For Vibrothermography, Jeremy Blake Renshaw, Stephen D. Holland, R. Bruce Thompson, David J. Eisenmann

David Eisenmann

Synthetic defects are an important tool used for characterizing the performance of nondestructive evaluation techniques. Viscous material‐filled synthetic defects were developed for use in vibrothermography (also known as sonic IR) as a tool to improve inspection accuracy and reliability. This paper describes how the heat‐generation response of these VMF synthetic defects is similar to the response of real defects. It also shows how VMF defects can be applied to improve inspection accuracy for complex industrial parts and presents a study of their application in an aircraft engine stator vane.


Quantification Of Toolmarks, L. Scott Chumbley, David J. Eisenmann, M. Morris, S. Zhang, J. Kreiser, J. Craft, C. Fisher 2016 Iowa State University

Quantification Of Toolmarks, L. Scott Chumbley, David J. Eisenmann, M. Morris, S. Zhang, J. Kreiser, J. Craft, C. Fisher

David Eisenmann

No abstract provided.


Forensic Examination Using A Nondestructive Evaluation Method For Surface Metrology, David J. Eisenmann, L. Scott Chumbley 2016 Iowa State University

Forensic Examination Using A Nondestructive Evaluation Method For Surface Metrology, David J. Eisenmann, L. Scott Chumbley

David Eisenmann

The objective of this paper is to describe the use of a new technique of optical profilometry in a nondestructive, non‐contact fashion for the comparison of two metallic surfaces, one hard and one soft. When brought in contact with one another, the harder material (i.e. the tool) will impress its surface roughness onto the softer. It is understood that the resulting set of impressions left from a tool tip act in a manner similar to a photographic negative, in that it leaves a reverse, or negative impression on the surface of a plate. If properly inverted and reversed ...


Flourescent Penetrant Inspection—Cleaning Study Update, David J. Eisenmann, Lisa H. Brasche 2016 Iowa State University

Flourescent Penetrant Inspection—Cleaning Study Update, David J. Eisenmann, Lisa H. Brasche

David Eisenmann

Fluorescent penetrant inspection (FPI) is widely used in the aviation industry and other industries for surface‐breaking crack detection. As with all inspection methods, adherence to the process parameters is critical to the successful detection of defects. There is variety of lubricants and surface coatings used in the aviation industry which must be removed prior to FPI. Before the FPI process begins, components are cleaned using a variety of cleaning methods which are selected based on the alloy and the soil types which must be removed. It is also important that the cleaning process not adversely affect the FPI process ...


From Xst To F-117a, Alan Brown 2016 Embry-Riddle Aeronautical University

From Xst To F-117a, Alan Brown

ERAU Prescott Aviation History Program

Learn the remarkable story of stealth technology from the man often referred to as “Mr. Stealth.” From 1975-1989 Alan Brown was a member of Lockheed “Skunk Works”, becoming program manager & chief engineer for the F-117A Stealth Fighter from initial concept until the first production aircraft was built, 1978 to 1982. Hear the inside story of the many challenges faced by the stealth program and how they were solved.


Experimentation Of Mode I & Mode Ii Fracture Of Uni-Directional Composites And Finite Element Analysis Of Mode I Fracture Using Cohesive Contact, Joseph Daniel Garrett 2016 California Polytechnic State University, San Luis Obispo

Experimentation Of Mode I & Mode Ii Fracture Of Uni-Directional Composites And Finite Element Analysis Of Mode I Fracture Using Cohesive Contact, Joseph Daniel Garrett

Master's Theses and Project Reports

As the use of fiber-reinforced composites has increased over the decades, so has the need to understand the complexity of their failure mechanisms as engineers seek to improve the damage tolerance of composite laminated structures. One of the most prevalent and limiting mode of failure within composite laminates is delamination, since it not only reduces a structures stiffness and strength, but can be very difficult to detect without the use of special non-destructive equipment. Industry testing organizations have utilized several fracture tests in order to characterize the fracture toughness of composite materials under different loading conditions. For this research, ASTM ...


Evaluation Of Strain Distortion Correction Protocol Using Scanning Electron Microscopy And Digital Image Correlation, Alexandra Mallory, Alberto Mello, Michael Sangid 2016 San Diego State University

Evaluation Of Strain Distortion Correction Protocol Using Scanning Electron Microscopy And Digital Image Correlation, Alexandra Mallory, Alberto Mello, Michael Sangid

The Summer Undergraduate Research Fellowship (SURF) Symposium

Scanning electron microscopy in combination with digital image correlation (SEM-DIC) is a useful technique for measuring strain in materials at the micro-scale. In particular, it can be used to identify micro-scale strain localizations that are the precursor to material failure. While SEM produces high resolution images of the microstructure, the images also contain a large amount of distortion that, during DIC, will result in distorted strain values that require correction. In this project, a nickel-based alloy underwent cyclic mechanical fatigue at three different high temperatures to a targeted maximum strain. Scanning electron microscopy imaging was done on a 200x150μm area ...


Metamodels Of Residual Stress Buildup For Machining Process Modeling, Stuart B. McCrorie, Michael Sangid 2016 Purdue University

Metamodels Of Residual Stress Buildup For Machining Process Modeling, Stuart B. Mccrorie, Michael Sangid

The Summer Undergraduate Research Fellowship (SURF) Symposium

In the process of machining materials, stresses, called residual stresses, accumulate in the workpiece being machined that remain after the process is completed. These residual stresses can affect the properties of the material or cause part distortion, and it is important that they be calculated to prevent complications from arising due to the residual stresses. However, these calculations can be incredibly computationally intensive, and thus other methods are needed to predict the residual stresses in materials for quick decision-making during machining. By using metamodels - a method of representing data where few data points exist - we can achieve an accurate prediction ...


Statistical Impact-Echo Analysis Using Bag-Of-Echoes Model For Concrete.Pdf, Jiaxing Ye 2016 National Institute of Advanced Industrial Science and Technology

Statistical Impact-Echo Analysis Using Bag-Of-Echoes Model For Concrete.Pdf, Jiaxing Ye

Jacky Yin

In recent years, advancement in information technologies, i.e. cloud service and high speed wireless network, greatly facilitate the large collection of structural health monitoring (SHM) data. In order to effectively exploit massive sensor data for accurate condition assessment of infrastructures, there has been increasing interest in application of statistical pattern recognition methods in the field of SHM. This paper addresses development of efficient pattern analysis scheme for impact-echo test, which is one of the most conventional nondestructive test (NDT) methods. The proposed scheme stems from Bag-of-feature (BoF) model, which has been successfully applied for natural language processing and computer ...


Statistical Impact-Echo Analysis Using Bag-Of-Echoes Model For Concrete.Pdf, Jacky Yin 2016 Hongkong Baptist university

Statistical Impact-Echo Analysis Using Bag-Of-Echoes Model For Concrete.Pdf, Jacky Yin

Jacky Yin

In recent years, advancement in information technologies, i.e. cloud service and high speed wireless network, greatly facilitate the large collection of structural health monitoring (SHM) data. In order to effectively exploit massive sensor data for accurate condition assessment of infrastructures, there has been increasing interest in application of statistical pattern recognition methods in the field of SHM. This paper addresses development of efficient pattern analysis scheme for impact-echo test, which is one of the most conventional nondestructive test (NDT) methods. The proposed scheme stems from Bag-of-feature (BoF) model, which has been successfully applied for natural language processing and computer ...


Ultrasonic Sol-Gel Arrays For Monitoring High-Temperature Corrosion, Thomas J. Eason, Leonard J. Bond, Mark G. Lozev 2016 Iowa State University

Ultrasonic Sol-Gel Arrays For Monitoring High-Temperature Corrosion, Thomas J. Eason, Leonard J. Bond, Mark G. Lozev

Center for Nondestructive Evaluation Conference Papers, Posters and Presentations

Corrosion of oil refinery equipment operating at high temperature is a growing challenge linked to an increase in sulfur concentration and acidity within the world supply of crude oils. Improved high temperature monitoring tools are needed to continuously measure the local minimum wall thickness of steel pipe subject to non-uniform internal corrosion. Thickness measurements must be sufficiently accurate to calculate the maximum allowable stress permissible as to avoid failure. Thickness measurements must also be sufficiently reliable and precise to correlate the rate of wall-loss with process conditions as to improve future corrosion rate predictions. Permanently installed structural health monitoring (SHM ...


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